Perforating apparatus



Jan.

1957 P. H. TAYLOR 2,778,426

PERFORATING APPARATUS Filed Sept. 4, 1953 IN V EN TOR.

iteti States PERFORATING APPARATUS Paul H. Taylor, Grand Island, N. Y., assignor to Wales- Strippit (Corporation, North Tonawauda, N. Y., a corporation of New York Application September 4, 1953, Serial No. 378,545

8 Claims. (til. 164-410) atent as disclosed in the Wales U. S. Patent No. 1,955,866,

granted April 24, 1934, and assigned to the assignee of the present application, the downward working stroke of the press ram stores energy in a wound steel wire spring, which forms part of the perforating unit; and this spring operates to withdraw the punch from the work after the perforating stroke is completed. The work, which these perforating implements can do, is limited, however, by the capacity of the steel spring used for stripping. To punch maximum thicknesses of stock material a heavy steel stripping spring has to be used. Such a spring increases the overall width of the perforating unit which in turn limits the closeness perforating units can be positioned to one another, thereby limiting the closeness at which adjacent holes can be punched in a single perforating operation. As a result the stripping units of perforating implements such asdi'sclosed in the Wales patent mentioned are frequently overloaded with the result that early failure occurs. It is also necessary with perforating units such as disclosed in the Wales patent mentioned to sharpen the punch frequently, or to assist sticking punches to strip by striking the work with a mallet, because the nature of the loads on the stripping spring made it impossible to strip a dull punch from a workpiece.

Another limitation on perforating units, such as, shown in the Wales patent mentioned, has been the. necessity of limiting the material to be punched to one-eighth inch thickness if a standard punch press is to be used, since, where work of more than one-eighth inch thickness is to be punched, stripping requirements demand springs of such size that a single stripping spring is impractical for standard press shut-heights. Special types of punch presses have had to be designed, where it was desired to punch material of more than one-eighth inch thickness on given hole centers.

The closeness of the hole centers and the thickness of the material which can be punched are, therefore, ordinarily governed by the best stripping spring punch compromise which can be made between the holder width and the necessary stripping force. This means that for many jobs two or three operations are necessary to punch holes on given centers in a material of a given thickness.

To overcome this difficulty, perforating units were developed, such as disclosed in Wales U. S. Patents Nos.

2,778,426 Patented Jan. 22, 1957 ice large diameter holes close to one another. These units are, therefore, particularly adapted to the close hole spacing especially required in the fabrication of aircraft. However, the arrangement of the springs in these units makes the punch element itself extremely fragile, and thin, and subject to considerable bending because, in order to clear the springs and still keep within the limited holder width, the punch must be made in long, slender columnar form. Furthermore, to avoid breakage of the punch at the juncture of its head and its body, its head must be drawn to make it less brittle. This, however, means an additional operation, and even so, the punch is still liable to bending and breakage. These units are ordinarily limited to punching a hole of a maximum diameter of 1 through A" thick stock. These units, furthermore, are of greater height than can be used in a press having a standard shut height, which means that their use has been confined tolarge expensive presses with greater open height. in addition, these units are costly because they require accurate and delicate assembly.

One object of the present invention is to provide a perforating unit which is narrow in width, and which can, therefore, be used with other similar units to punch holes on close centers, but which is capable of perforating large diameter holes on close centers through, thicker gauge metal than can be punched. with units such as disclosed in Patents Nos. 2,326,588 and 2,355,344 above mentioned.

Another object of the invention is to provide a selfcontained perforating unit having a novel stripping medium, a medium which simplifies the unit structure and which is low in cost and which can readily be fabricated. I

Another object of the invention is to provide a selfcontained perforating unit which may be used with either punch presses of normal shut heights or with punch presses of special design having larger shut heights, there'- by reducing the inventory of punch units required and providing a single unit which will serve two purposes and which is more or less universal in its adaptability.

, Another object of the invention is to provide a selfcontained perforating unit which has stripping 'forces more than adequate for the job with the result that the punch is not overloaded and does not need to be sharpened as frequently as heretofore, and with the further result that mallets or other types of percussion implements do not have to be used to assist in stripping the work from the punches when stuck.

A further object of the invention is to provide a self contained perforating unit which will have a life many times that of perforating units employing mechanical springs.

A further object 'of the invention is to provide a stripping medium of reduced weight and volume so that its mass is substantially less than that of stripping means used in conventional punches with the result that the cycling frequency can be higher than with a conven tional punch and stripping spring.

' Another object of the invention is to provide a selfcontained perforating unit wherein the punch head, against which stripping takes place, is but slightly larger than the stock of the punch, and which permits of use 2,326,588, granted August 10, 1943, and 2,355,344,

granted August 8, 1944, in which a series of springs are arranged in tandem above the holder. These units can be made of extremely narrow width sothat they are adapted to be placed side by side in contiguity to punch of a punch that can be finished simply by grinding hardened bar stock instead of requiring the more complicated process of machining and then grinding. I

A further object of the invention is to provide'a self- 5 A still further object of the invention is to provide a self-contained perforating unit which permits the use of a punch having a rigid punch body throughout the spring area.

A still further object is to provide a self-Contained punch unit which permits the use of a punch of uniform hardness.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawing:

Fig. 1 is a side elevation in partial section of a perforating implement made according to one embodiment of this invention;

Fig. 2 is a top plan view of this unit; and

Fig. 3 is asection taken on the line 33 of Fig. 1 looking in the direction of the arrows.

The self-contained perforating unit shown in the drawis of the general type shown in the patents above mentioned. It comprises a C-frame having parallel upper and lower arms 11 and 12. Mounted on the lower arm 12 of the frame is a die member 14. This die member may be of conventional construction, having a die opening 15 therein and being relieved below said die open ing, as indicated at 16, to provide a discharge passage or chute through which the slugs punched from the Work are discharged.

Mounted in the upper arm 11 of the frame is the punch assembly 20. This is mounted in axial alignment with the die member. This assembly comprises a stepped, tubular member 21 having a lower tubular section 22 of relatively small diameter and an upper tubular section 24 of larger diameter. 1

The lower tubular section 22 of member 21 is mounted in the upper arm 11 of the Q-frame. It has a cylindrical bore; and it supports and guides the punch 25. The upper tubular section 24 of member 21 contains and holds a compressible solid plastic 27 which acts as the stripping medium for the punch. This plastic may be a hard, dense silicone, namely a polysiloxane elastomer, although other compressible solid plastics, such as lucite, polystyrene, cellulose acetate, nylon, etc., can also be employed, dependingon the loads encountered.

The punch itself has a head 28 of enlarged diameter as compared with its shank portion 29; and this head is connected to the shank portion 29 by an intermediate conical section 30 which blends smoothly with both head 28 and shank 29. The perforating unit is adapted to be mounted between the bed and ram 36 of a punch press. The compressible plastic member 27 may be shaped initially to receive the shank 29 and conical section 30 of the punch; and the conical section 30 and head 28 of the punch act against the compressible stripping medium 27 when the punch is forced by the ram 36 on its downstroke through the sheet metal plate 37 or other workpiece that is to be perforated.

The stripping medium is preferably preloaded in use. This is accomplished by dimensioning the perforating unit so that even when the ram 36 is in withdrawn position, the ram will exert a pressure on the head of the Punch and through the punch on the compressible plastic 27 to distort the plastic and cause the plastic, which is somewhat elastic, to fill the bore of the enlarged section 24 of stepped tubular member 21. When the ram 36 moves downwardly on its working stroke, then, the head 28 of the punch and its conical section 30' will act against the compressible solid 27 causing a reduction in volume therein, and storing energy which, upon withdrawal of the ram on its return stroke, will withdraw the punch from the work.

In order to prevent extrusion of the stripping material 27 from the lower end of the chamber 24 a suitable plastic seal 40 made, for instance, of nylon is provided in the lower end of the chamber 24. This s,ealing eollar 40 is mounted in a recess 41 in tubular member 21 and may be slightly oversize so that it has to be compressed to be forced therein. It has a close fit with shank 29 of the punch and acts as a guide therefor. A somewhat similar sealing member 4-2 made of nylon or other suitable plastic is provided at the upper end of the chamber 24 to prevent extrusion of the compressible plastic 27 through the upper end of chamber 24. This sealing member may have coaxial conical ribs 43 and 44 on its underside around its bore and its periphery, respectively, to assist in distribution of the stresses equally throughout the stripping medium 27. While the seal 4% is supported against extrusion itself by the tight fit of the shank of the punch with the cylindrical section 22 of tubular member 21 which supports the punch shank, the upper nylon seal 42 must be supported by a steel washer 45 or the like which prevents extrusion. This washer 45 is interposed between the closed upper end of tubular section 24 and seal 42.

As previously described, the punching force is transmitted from the ram 36 to the punch 25. During the first part of the working stroke the punch carries the stepped tubular member 21 along with it through the intermediary plastic 27, the coil lifter spring 50 being compressed. This spring surrounds the tubular member 21 and. is interposed between a shoulder 51 on the exterior of tubular member 21 and the upper face 52 of upper arm 11 of the G-frame. When the tubular member 21 engages the sheet metal plate 37, or other workpiece which is to be perforated, however, the downward movement of tubular member 21 and of the stripping material 27 is halted. Then as the punch moves through the work, effecting the perforating operation, the compressible plastic 27 is compressed and reduced in volume, storing energy, which, when released by the return movement of the ram, forces the punch upwardly to withdraw it, that is, to strip it from the work. The punch assemblage 20 is then returned to its upper position by the coil lifter spring 50.

With a perforating unit of the construction described holes of relatively large diameter can be punched on close centers. For instance, whereas the units of Patents Nos. 2,326,588 and 2,355,344 require three springs and a complicated punch and stripper combination to punch a maximum 1 diameter hole through /s" thick stock, the perforating unit of the present invention can punch a /8" diameter hole through the same thickness of stock and on the same centers. This is because of the greater stripping effectiveness attainable through use of a compressible solid plastic stripping medium.

One feature of the device of the present invention is the action of the conical section 30 of the punch. As the punch moves downwardly under working load its conical section 3.0 stresses the plastic 27 equally in all directions. Therefore a relatively long punch stroke is possible for a unit of a given height.

The punch 25 with its conical transition portion 30 can be hardened for its whole length. Its head does not have to be drawn or annealed as has the head of a conventional punch in which the head and the shank portions of the punch join at an abrupt shoulder. The present invention permits, therefore, of use of a stronger punch, and one less likely to break than prior constructions, and also one which can be made without annealing.

While other materials than hard silicones may be utilized in a spring made according to this invention it is economically desirable to use materials having the greatest compressibility, such as hard silicones, which, as stated, have a minimum compressibility of about 6%. In addition, there is another reason for using silicones, that is, in the operation of a perforating unit made according to the present invention, the working of the solid material therein will of necessity produce heat. Silicones have a natural resistance to high heat and their use in a unit of the character herein described is particularly advantageous because silicones do not deteriorate from heat, and heat does not have any deleterious effects on such materials even in the presence of the lubricants used. I

The seals are made preferably of nylon or a similar material, when a silicone solid is used in the unit, because it has been found that the silicones tend to cause seizure and scoring when they get between relatively movable parts made of ferrous material, whereas nylon remains unaifected.

While the invention has been described in connection with a particular embodiment thereof and a particular use therefor, then, it will be understood that it is capable of further modification and use, and that this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim 1. Punching apparatus comprising a support, a tubular stripper member reciprocable in said support, said stripper member having a tubular guide portion at one end whose bore is of relatively small diameter, said stripper mem-' ber being formed with a chamber adjoining said guide portion and axially aligned with the bore of said guide portion, said chamber being of larger internal diameter than the bore of said guide portion, a punch having a shank of relatively small diameter, a head of larger diameter, and an intermediate conical portion connecting said head and said shank, said shank being reciprocable in said bore and being guided thereby, and said head being reciprocable in said chamber, and a compressible solid stripping medium surrounding said head and said conical portion and filling the space in said'chamber around said punch.

2. A self-contained perforating unit comprising a C-frame, a die member carried by the lower arm of said frame, a tubular stripper member reciprocable in the upper arm of said frame, said stripper member having a tubular guide portion at one end and an enlarged chamber adjoining said guide portion, a punch reciprocable in said st-rippermember, said punch having an enlarged head, a cylindrical shank and a conical portion connecting said head and shank, said stripper member being closed at both ends except for axially aligned openings through which opposite ends of said punch pass, the shank portion of said punch being reciprocable in said guide portion of said stripper member and being guided thereby, and a compressible solid stripping medium in said chamber surrounding said punch and interposed between said head, said conical portion and said stripper member and filling the space in said chamber around said punch.

3. A self-contained perforating unit comprising a C-frame, a die member carried by the lower arm of said frame, a stepped tubular stripper member having a cylindrical portion provided with a cylindrical bore reciprocable in the upper arm of said frame and having a chamber of larger outside and inside diameters than said cylindrical portion disposed above said outer arm, a punch having a shank of relatively small diameter, an enlarged head, and a conical section connecting said shank and head, said shank being cylindrical and reciprocable in said cylindrical bore and being guided thereby, and a compressible solid stripping element mounted in said chamber and surrounding said conical section and filling the space in said chamber about said conical section.

4. A self-contained perforating unit comprising a C-frame, a die member carried by the lower arm of said frame, a stepped tubular stripper member having a cylindrical portion provided with a cylindrical bore reciprocable in the upper arm of said frame and having a chamber of larger outside diameter than said cylindrical portion disposed above said outer arm, a punch having a shank of relatively small diameter, an enlarged head, and a conical section connecting said shank and head, said shank being cylindrical and reciprocable in said cylindrical bore and being guided thereby, and a compressible solid stripping element mounted in said chamber and surrounding said conical section and filling the space in said chamber about said punch, and a coil lifting spring surrounding said cylindrical portion of said stripper member and interposed between said chamber and said upper arm.

5. A self-contained perforating unit comprising a Cframe, a die member carried by the lower arm of said frame, a stepped tubular stripper member, said stripper member having a cylindrical portion of reduced diameter reciprocable in the upper arm of said C-frame and a portion of larger diameter disposed above said upper arm, said cylindrical portion of reduced diameter having a cylindrical bore and said portion of larger diameter having a chamber therein, a reciprocable punch, said punch having a cylindrical shank reciprocable in said bore and guided thereby, an enlarged head projecting outwardly through the upper end of said chamber, and a conical section connecting said shank and said head, a compressible plastic stripping element disposed in said chamber around said conical portion and preloaded to completely fill said chamber, and sealing means at opposite ends of said chamber to prevent extrusion of said stripping element from said chamber, said sealing means forming guides for said punch in its reciprocation.

6. A self-contained perforating unit comprising a C- frame, a die member carried by the lower arm of said frame, a stepped tubular stripper member, said stripper member having acylindrical portion of reduced diameter reciprocable in the upper arm of said C-frame and a portion of larger diameter disposed above said upper arm, said cylindrical portion of reduced diameter having a cylindrical bore and said portion of larger diameter having a chamber therein, a reciprocable punch, said punch having a cylindrical shank reciprocable in said bore and guided thereby, an enlarged head projecting outwardly through the upper end of said chamber, and a conical section connecting said shank and said head, a compressible plastic stripping element disposed in said chamber around said conical portion and preloaded to completely fill said chamber, and sealing means at opposite ends of said chamber to prevent extrusion of said stripping element from said chamber, said seal-ing means forming guides for said punch in its reciprocation, and a coil lifting spring surrounding said cylindrical portion of reduced diameter and interposed between said portion of larger diameter and said upper arm.

7. Punching apparatus comprising a member having a chamber formed therein and having a tubular guide portion at one end of said chamber, a punch reciprocable in said chamber and having cylindrical sections at opposite ends of diiferent diameter, respectively, which project through opposite ends of said chamber, said punch having a conical section within said chamber connecting said cylindrical sections, the cylindrical section of smallor diameter reciprocating in said tubular guide portion and being guided thereby, and a compressible solid plastice stripping medium disposed in said chamber around and in engagement with said conical section and filling said chamber, and sealing members disposed at opposite ends of said chamber to prevent extrusion of said stripping medium from said chamber and acting as guides for said punch.

8. Punching appaua-tus comprising a member having a chamber, a ferrous metallic punch reciprocable in said chamber and having cylindrical sections at opposite ends of dilferent diameter, respectively, which project through opposite ends of said chamber and having a conical section within said chamber connecting said cylindrical sections, a hard, dense silicone stripping element disposed in said chamber around and in engagement with said conical section andfil ling said chamber, and sealing members disposed at opposite ends of said chamber to prevent ext-rustion of said stripping element from said chamber and acting as guides for said punch, said sealing members being made of nylon.

References Cited in the file of this patent UNITED STATES PATENTS 20,846 Granger July 6, 1858 8 Clark Apr. 30', @anet Mar. 14, Grissom July 20, Wales Apr. 24, Moran Jan. 28, Dewey Apr. 18, Wales Nov. 28, Albert et a1. V June 3, Becker June 10; Granberg July 31, 

